Die grinder

ABSTRACT

A grinder includes a drive tube dimensioned to slideably receive an elongated, generally cylindrical grinding element, such as a bonded grinding wheel or coated abrasive roll; and locking means for releasably locking the grinding element for rotation with the drive tube. When a protruding end of the grinding element becomes worn, an additional length of grinding element may be withdrawn from within the drive tube.

United States Patent WeIsch [451 Mar. 18, 1975 DIE GRINDER Primary ExaminerJames L. Jones, Jr.

t l N. l h T d [75] [men or wa ter We Sc Onawan a N Y Attorney, Agent, or Firm-Bean & Bean [73] Assignee: Dynabrade lnc., Tonawanda, NY.

[22] FiIed: Aug. 27, 1973 [21] Appl. No.: 391,686 [57] ABSTRACT 52 1.5. CI. f 51/170 PT, 279/1 Q A grinder includes a drive tubedimensimled Slide- 511 Int. Cl B24b 23/00 ably receive an elongated, generally Cylindrical grind- [58] Field of Search 51 /170 PT, 263, 71; ing element, Such as a bonded grinding Wheel of 285/348. 279/1 Q 102 103 coated abrasive roll; and locking means for releasably locking the grinding element for rotation with the [56] References Cited drive tube. When a protruding end of the grinding element becomes worn, an additional length of grinding UNITED STATES PATENTS element may be withdrawn from within the drive tube. 2,359,594 10/1944 Turenchalk et a1 51/170 PT FOREIGN PATENTS OR APPLICATIONS 11 Claims, 6 Drawing Figures 112,910 4/1961 Denmark 285/348 54 1e 12 24 16 16b 52 5O A I \L i m g DIE GRINDER BACKGROUND OF THE INVENTION Commercially available grinding elements, such as bonded wheels (i.e., mounted points) and cartridge rolls (i.e., coated abrasive wrapped rolls) of the type adapted to be used with powered grinding tools are formed around a metal reinforcing drive spindle, which is dimensioned to be gripped by the chuck of the tool. A drawback of these grinding elements is that they must normally be thrown away whenever a portion thereof is worn away sufficiently to expose the embedded end of the drive spindle, even though substantial portions of otherwise useable grinding material remain intact. This, coupled with the fact that long grinding elements of this type are normally subject to severe vibration during use, has led to the common practice of forming such grinding elements with a relatively short axial length, eg 2 inches or less; thus ofttimes requiring several grinding element replacements during a single grinding operation.

SUMMARY OF THE INVENTION The present invention is directed towards a grinding tool employing a novel drive mechanism permitting the utilization of substantially the whole of the length of a relatively long grinding wheel or cartridge of the type presently available for manual use without subjecting the working end thereof to severe vibration or bending conditions. Grinding elements of this type have a relatively uniform diameter, are available in lengths of upwards of about 6 to 8 inches, and are not formed with an imbedded drive or reinforcing spindle.

More specifically, the grinding tool of the present invention basically includes a drive tube, which is dimensioned to slideably receive the elongated grinding element; and means for releasably locking the grinding element for rotation with the drive tube. As the end of the grinding element, which protrudes from the forward end of the tube becomes worn, the locking device may be released to permit an additional length of the grinding element to be withdrawn from within the tube.

In accordance with a first embodiment of the present invention, the locking device includes a ring member, such as an O-ring, which is disposed about the grinding element and adapted to be resiliently deformed into firm clamping engagement therewith for the purpose of releasably locking or coupling the grinding element for rotation with the drive tube. The ring member is deformed by being clamped axially intermediate the front end of the drive tube through which the grinding element projects and a sleeve bushing by means of a clamping member, which is adjustably fixed to the front of the drive tube, as by screw threads. The bushing includes a sleeve portion, which is preferably formed of a relatively hard abrasive resistant plastic material, and sized to be slideably fitted over the grinding element and to project through the clamping member for the purpose of providing support for the projecting end of the grinding element forwardly of the point at which it is clamped by the ring member. The sleeve portion serves to prevent wearing away of the clamping member and to dampen vibration of the projecting end of the grinding element.

In a second embodiment of the present invention the O-ring clamping element is dispensed with and the sleeve bushing employed to resiliently clamp the grinding element for rotation with the drive tube. In this construction, the sleeve bushing and the clamping member are formed with essentially conically shaped camming surfaces, which cooperate to resiliently deform the sleeve bushing into frictional engagement with the grinding element, when the clamping member is threaded onto the drive tube.

The maximum diameter of grinding element employed within a given grinding tool is limited by the requirement that it be freely insertable within the drive tube. However, grinding elements of smaller diameter may be employed in the same grinding tool by employing an adapter assembly including a filler or reducing sleeve, which is adapted to be slideably fitted within the drive tube and in turn formed with a bore opening dimensioned to freely receive the reduced diameter grinding element.

The adapter assembly may also be employed to drivingly couple a metal chuck spindle to the drive tube, thereby to permit the tool to be employed for driving diverse types of grinding and/or related tool elements.

DRAWINGS The nature and mode of operation of the present invention may be more fully described in the following detailed description taken with the accompanying drawings wherein:

FIG. 1 is a partially sectionalized side elevational view of a grinding tool embodying the present invention;

FIG. 2 is an exploded view of that part ofthe grinding tool included within the area designated as FIG. 2 in FIG. 1;

FIG. 3 is an exploded view similar to FIG. 2, but showing an adapter assembly for use in fitting the grinding tool with a reduced diameter grinding element;

FIG. 4 is a view illustrating an alternative locking device;

FIG. 5 is a sectional view taken along line 5-5 in FIG. 4; and

FIG. 6 is a view illustrating an alternative adapter assembly.

DETAILED DESCRIPTION A grinding tool formed in accordance with a first form of the present invention is designated as 10 in FIG. 1. Tool 10 generally includes a hollow metal casing or tool housing 12; a drive assembly or mechanism 14; a drive tube 16, which has a front end 16a arranged to extend outwardly through a casing front wall opening 18 and is dimensioned to freely accommodate an elongated, relatively uniform diameter cylindrical grinding element 20; a locking device 22 for releasably locking grinding element 20 for rotation with drive tube 16; a ball bearing or other suitable bearing device 24 for mounting drive tube 16 for rotation within casing 12; and a manually operable latch device 26, which is fitted within casing bottom wall opening 28 for selectively constraining rotation of drive tube 16.

While the grinding tool of the present invention is not limited to the utilization of any specific drive assembly, assembly 14 is shown in FIG. 1 for purposes of illustration as including a power source, such as an air motor 30, which is suitably affixed to casing rear wall 32 and drivingly connected through a casing rear wall opening 34 to a drive pulley 36 arranged within casing 12; pulley 36 being coupled to the rear end 16b of drive tube 16 by means of an endless belt 38. The tension in belt 38 may be selectively controlled by a casing rear wall mounted belt take up or idler pulley 40. Motor 30 may have any suitable shut off or speed control, such as may be afforded by a pivotally supported lever 42, which is adapted to be squeezed by the hand of an operator during use of the grinding tool. Also, the surface of drive pulley 36 and the surface of drive tube rear end 16b would preferably be slightly crowned in order to insure proper belt tracking.

In the illustrated construction, air motor 30 serves as a convenient hand grip for manipulating tool 10. However, if desired, casing 12 may be shaped to define a convenient hand grip, such as a pistol grip.

It will be understood that the specific construction of grinding element forms no part of the present invention. However, it is anticipated that such grinding element will either be in the form of a bonded grinding wheel, which is known as a mounted point, or a cartridge roll, which is formed by winding or wrapping a coated abrasive material. Each of these products, which are presently available for use in manual grinding operations, are characterized as being of an elongated, essentially cylindrical configuration and as being substantially wholly usable in that a reinforcing insert of a dissimilar material, e.g., a steel spindle, is not imbedded therein.

Locking device 22 is best shown in FIG. 2 as including a clamping member 50; a sleeve bushing 52; and a resiliently deformable ring member, such as a rubber or urethane O-ring 54.

Clamping member 50, which may be characterized as being of a generally cup-shaped configuration, has an internally threaded rim portion 56 by which it may be adjustably and removably mounted on drive tube front end 160 and an opening 58 extending axially through its radially extending base wall portion 60.

Bushing 52 includes a sleeve portion 62, which is removably slide fitted within clamping member opening 58 and formed with an axially extending through bore opening 64 dimensioned to freely or loosely receive the projecting or working end 20a of grinding element 20; and an enlarged base portion 66 dimensioned to be removably received within clamping member 50 for engagement with its base wall portion 60. Base portion 66 is shown in FIG. 2 as being of two part construction including a front part 67, which is formed integrally with sleeve portion 62 and a separately formed rear part or washer 68, which may, if desired, be adhesively bonded or otherwise fixed to the rearwardly facing surface of front part 67. In the illustrated construction, sleeve portion 62 and front part 67 are formed from a relatively hard, wear resistant plastic material, such as a urethane of from between about 70-90 Durometer (Shore A) and washer 68 is formed of metal. Although the plastic material employed is relatively hard, it can still be properly considered to be resiliently deformable. Further, the rearwardly facing surface of washer 68 is shown as being shaped to define a rearwardly and outwardly flared or conically shaped guide surface 69 arranged for engagement with O-ring 54. Alternatively, guide surface 69 may be defined by the forwardly facing surface of drive tube front end 16a.

It would appear that washer 68 may be dispensed with when the plastic material forming sleeve portion 62 and front part 67 is in the higher range of hardness now contemplated. In this case, it is contemplated that either one of the facing surfaces of drive tube front end 160 and front part 67 may define guide surface 69.

As will be apparent from viewing FIGS. 1 and 2, when clamping member 50 is moved towards, that is threaded onto, drive tube front end 16a, O-ring 54 is clamped or axially compressed between sleeve bushing 52 and drive tube from end 16a, such that the O-ring is radially deformed into surface clamping engagement with grinding element 20 intermediate its ends; the O- ring being properly constrained or guided radially into engagement with the grinding element by guide surface 69. Preferably, when O-ring 54 is in an unclamped state, its internal dimension is such as to snugly grip the cylindrical surface of grinding element 20, whereby the O-ring may be rolled lengthwise of the grinding element to facilitate lengthwise directed adjustments of the grinding element relative to drive tube 16.

Again referring to FIG. 1, it will be understood that latch device 26 is employed to releasably constrain rotation of drive tube 16, during threading and unthreading movements of clamping member 50. To this end, latch device 26 includes a plunger operator 70, which may be manually depressed against the return bias of a coil spring 72 for receiptwithin a drive tube wall aperture 74.

Again referring to FIG. 1, it will be noted that the rear wall of tool 10 may also be formed with an opening disposed in alignment with drive tube 16 and that a cup-shaped guard member 82 may be fixed to the rear wall of the casing, as by screw devices 84, in alignment with opening 80, whereby to permit the rear of the grinding element to project rearwardly of the casing without creating a hazard for the operator of the tool. Opening 80 and guard 82 would, of course, have diameters equal to and preferably in excess of the internal diameter of the drive tube in order to prevent abrading contact with the grinding element with the casing or the guard. By this arrangement, a relatively small conveniently handled casing having a relatively short drive tube is adapted to accommodate a relatively long grinding element. When extra long grinding elements are to be employed, a sleeve of plastic material, not shown, may be used to center the rear end of the grinding element relative to the drive tube and for vibration cushioning purposes. Alternatively, it is anticipated that the internal surface of a metal drive tube could be formed with a coating or covering of vibration damping material and that for certain uses the drive tube itself formed wholly of a plastic composition.

Since grinding element 20 is not formed with any reinforcing insert, its unsupported projecting end 20a would normally not be allowed to project more than about two inches beyond clamping member 50 during a grinding operation. When projecting end 20a is worn away to an extent where the clamping member might engage with a workpiece, grinding would be momentarily halted and a new length of grinding element removed from within the drive tube by removing the clamping member. rolling the O-ring back along the surface of the grinding element and re-applying the clamping member to again constrain the grinding element for rotation with the drive tube. This procedure may be repeated as long as a sufficient length of grinding element remains to be gripped by the O-ring. As a result, all but a relatively short length of the grinding element may be effectively used for grinding purposes.

It is anticipated that during the grinding operation, the side of projecting end a will normally be applied to the workpiece much in the same manner as with conventional power tool operated grinding elements, such that the projecting end will be progressively worn away to assume an essentially conically shaped configuration. Since the grinding element employed in the practice of the present invention is not intentionally provided with any reinforcing insert, this sidewise pressure tends to bend or slightly deflect projecting end 20a into positive bearing contact with sleeve portion 62. While there is no intentional relative rotation between the grinding element and sleeve portion 62, some relative rotation may occur. This, coupled with normal vibratory movements of the projecting end 20a, will serve to cause a wearing away of the wall of sleeve portion 62 until the front end of opening 64 develops a conical configuration. At some point, the sleeve portion is no longer effective to properly constrain deflection and cushion vibrations of projecting end portion 20a and the latter may fail in bending. Before the sleeve portion 62 is worn to a point where failure might occur, the grinding operation would be halted and sleeve bushing 52 replaced. It would appear that, while sleeve portion 62 could be formed ofa relatively soft or pliable plastic or rubber and still be effective in dampening vibrations of the grinding'element, it would not be practical from the standpoint of service life or more importantly, from the standpoint of being able to properly constrain bending deflections of the grinding element. On the other hand, if sleeve portion 62 were incorporated as part of the clamping member and formed of metal, it would, of course, serve to constrain deflections of projecting end 20a. However, this would be impractical from a cost standpoint and be ineffective in reducing or cushioning vibrations. Accordingly, the most practical form of the present invention, as now contemplated, would feature a disposable plastic sleeve protion or busing, which is arranged forwardly of the O-ring and formed of a material which is sufficiently hard to both resist wear and prevent excessive deflections of pro-' jecting end 20a, while being sufficiently soft to dampen vibrations of the projecting end.

Reference is now made to FIG. 3, wherein there is shown an adaptor assembly 90 adapted for use in fitting the above disclosed grinding tool with a grinding element of reduced diameter. By viewing FIG. 3, it will be apparent that assembly 90 includes a sleeve bushing 52' and a resiliently deformable ring member, such as a rubber O-ring 54', which are of identical construction and function to similar parts previously described above with reference to FIGS. 1 and 2, except that their through openings are sized to accommodate reduced diameter grinding element. However, it will be noted that particularly with assemblies adapted for use with smaller sized grinding elements, sleeve portion 62' may be substantially elongated so as to afford support for projecting end 20a forwardly of clamping member 50.

Assembly 90 additionally includes a filler or reducing sleeve 92, which is dimensioned to be removably insertable within drive tube 16 and to freely accommodate the reduced diameter grinding element therewithin. The front end portion 920 of reducing sleeve 92 is enlarged to define a radial surface dimensioned to axially abut against drive tube front end 16a inwardly of its outer surface; the forwardly facing surface of front end portion 92a cooperating with sleeve bushing 52 to clampingly deform O-ring 54' for the purpose of constraining the grinding element for rotation withdrive tube 16. Reducing sleeve 92 may selectively be formed from metal or plastic.

Reference is now made to FIG. 4, where an alternative or simplified locking device construction is designated as and shown as generally including a clamping member 50a and a resiliently deformable sleeve bushing 52a, which cooperate to constrain grinding element 20 for rotation with drive tube 16. It will be noted that the previously described ring member is dispensed with in the construction illustrated in FIG. 4.

Clamping member 50a is similar to previously described clamping member 50, except that its base wall portion 60a is shaped to define a conically shaped camming or pressure surface. As a practical matter, bushing 52a may be considered as including a sleeve portion 620, which is formed with an axially extending through opening 64a dimensioned to freely or loosely receive grinding element projecting end 20a; and an enlarged base portion 66a, which is dimensioned to be removably received with clamping member 50a for engagement with base wall portion 60a. In a preferred construction, the forwardly facing cam follower surface 66b of base portion 66a, which engages with base wall portion 60a, is ofa like conically shaped configuration and has its forward end disposed coincident with the forward end of sleeve portion 62a. However, it is anticipated that the sleeve portion may project forwardly of this latter conical surface in order to permit it to extend completely through openings 58a to a point forwardly of the clamping member.

By viewing FIG. 5, it will be appreciated that the il lustrated construction of bushing 520 also departs from the construction of bushing 52 in that sleeve portion 62a is formed with a plurality of slots 102, which extend lengthwise of and open radially inwardly towards sleeve portion opening 64a.

As will be apparent from viewing FIG. 4, when clamping member 50a is moved towards, that is, threaded onto drive tube front end 160, bushing 52a is clamped for axially compressed therebetween; the cooperating conically shaped cam and cam follower surfaces of member 50 and bushing 52a additionally serving to direct or deform the bushing radially inwardly into clamping frictional engagement with the surface of grinding element 20a. Bushing 52a may be formed of a urethane having the same characteristics as the urethane described for use in connection with bushing 52. In this case, however, slots 102 and the cooperating cam surfaces insure radial deformation of bushing 52a to a degree sufficient to properly grip the grinding element.

Reference is now made to FIG. 6, wherein there is shown an alternative adapter assembly 110, which is adapted for use in fitting the grinding tool with a grinding element of a reduced size, not shown, or if desired. with a chuck spindle 112; the spindle being suitably connected to a conventional chuck 114 of the type adapted to mount diverse conventional grinding or polishing elements. Assembly includes a sleeve bushing 52a, which is identical in construction and function to bushing 52a, except that its through opening 64a is sized to receive a smaller sized grinding element or chuck spindle 112. Assembly 110 also includes a filler or reducing sleeve 92, which is identical in construction and function to sleeve 92 previously described with reference to FIG. 3. In this construction, the threading of member 50a onto drive tube 16 serves to clamp reducing sleeve front end portion 92a against drive tube front end 16a and to deformably clamp bushing 52a intermediate member-50a and front end portion 92a, whereby to couple spindle 112 for rotation with the drive tube.

I claim:

1. In a grinding tool adapted for use with an elongated relatively uniform diameter grinding element having an end adapted to be progressively worn away be engagement with a workpiece during operation of said grinding tool, the combination comprising:

a rotatably supported drive tube, said drive tube being dimensioned to freely accommodate said grinding element therewithin to removably extend through a front end thereof;

means for rotating said drive tube; and

locking means carried by said front end for releasably clamping said grinding element intermediate opposite ends thereof for rotation with said drive tube, whereby said end of said grinding element normally projects forwardly of said front end beyond said locking means during operation of said tool, said locking means including a deformable member formed or a resiliently deformable material and clamping means carried on said front end for resiliently deforming said deformable member into clamping surface engagement with said grinding element whereby to releasably clamp said grinding element for rotation with said drive tube, said clamping means including a cup shaped clamping member having an opening through a base portion thereof and sleeve means slidably receiving said grinding element and being arranged within said clamping member to extend forwardly through said opening, said clamping member having a rim portion threadably attached to said front end of said drive tube for releasably maintaining said sleeve means in deforming engagement with said deformable member, and said sleeve means being formed at least in part of a relatively hard abrasiveresistant plastic material thereby to cushion transversely directed vibratory movements of said end of said grinding element relative to said base portion of said clamping member forwardly of the point at which said grinding element is clampingly engaged by said deformable member.

2. In a grinding tool adapted for use with an elongated relatively uniform diameter grinding element having an end adapted to be progressively worn away by engagement with a workpiece during operation of said grinding tool, the combination comprising:

a rotatably supported drive tube;

means for rotating said drive tube; and

locking means carried by a front end of said drive tube for releasably clamping said grinding element intermediate opposite ends thereof for rotation with said drive tube, whereby said end of said grinding element normally projects forwardly of said front end beyond said locking means during operation of said tool, said locking means includes a reducing sleeve, a generally cup-shaped clamping member, and a sleeve bushing formed of a resiliently deformable material, said reducing sleeve being slidably and removably insertable within said drive tube and dimensioned to freely accommodate said grinding element therewithin to removably extend through a front end portion thereof, said front end portion defining a radial surface dimensioned to abut against said front end of said drive tube inwardly of an outer surface thereof,said brushing having a through opening dimensioned to loosely receive said grinding element and having a concentrically arranged cam follower surface, said clamping member being internally dimensioned to removably receive said bushing and said front end portion and having an opening through a base portion thereof sized to at least freely receive said grinding element, said clamping member base portion defining a cam surface, said clamping member having a rim portion adjustably threaded onto' said front end of said drive tube whereby to cooperate with said front end to axially clamp said bushing against said front end portionand said front end poortion against said front end of said drive tube, whereby said cam and cam follower surfaces cooperate to resiliently deform said bushing radially into clamping surface engagement with said grinding element and said grinding element and reducing sleeve are constrained for rotation with said drive tube.

3. In a grinding tool adapted for use with an elongated relatively uniform diameter grinding element having an end adapted to be progressively worn away by engagement with a workpiece during operation of 30 said grinding tool, the combination comprising:

a rotatably supported drive tube;

means for rotating said drive tube; and

locking means carried by a front end of said drive tube for releasably clamping said grinding element intermediate opposite ends thereof for rotation with said drive tube, whereby said end of said grinding element normally projects forwardly of said front end beyond said locking means during operation of said tool, said locking means including a reducing sleeve, a cup-shaped clamping member,

a sleeve bushing and an O-ring formed of resiliently deformable material, said reducing sleeve being slidably and removably insertable within said drive tube and dimensioned to freely accommodate said grinding element therewithin to removably extend through a front end portion thereof, said front-end portion defining a radial surface dimensioned to abut against said front end of said drive tube inwardly of an outer surface thereof, said sleeve bushing having a sleeve portion formed of a relatively hard abrasive-resistant plastic material and dimensioned to loosely receive said grinding element and an enlarged base portion, said clamping member being internally dimensioned to removably receive said enlarged base portion and said front end portion and having an opening through a base portion thereof for removably receiving said sleeve portion, said O-ring being arranged intermediate facing surfaces of said enlarged base portion and said front end portion and being dimensioned to snugly receive said grinding element, one of said facing surfaces having an essentially conically shaped guide surface arranged to axially engage said O-ring, said clamping member having a rim portion adjustably threaded onto said front end whereby to cooperate with said front end to axially clamp said front end portion against said front end and said O-ring between said guide surface and another of said facing surfaces for resiliently deforming said O-ring radially inwardly into clamping engagement with said grinding element and for clamping said reducing sleeve, sleeve bushing and grinding element for rotation with said drive tube, and said sleeve portion cushioning transversely directed vibratory movement of said end of said grinding element relative to said base portion of said clamping member forwardly of the point at which said grinding element is clampingly engaged by said O-ring.

4. In a grinding tool adapted for use with an elongated relatively uniformed diameter grinding element having an end adapted to be progressively worn away by engagement with a workpiece during operation of said grinding tool, which comprises in combination:

a hollow casing having an opening through a wall thereof;

an elongated drive tube, said drive tube being dimensioned to freely accommodate said grinding element therewithin to removably extend through a front end thereof;

means for supporting said drive tube for rotation within said casing with said front end of said drive tube projecting outwardly through said casing wall opening;

means for rotating said drive tube; and

locking means carried by said front end of said drive tube for releasably clamping said grinding element intermediate opposite ends thereof for rotation with said drive tube wherein said grinding element normally projects forwardly of said front end beyond said locking means during operation of said tool, said locking means includes a cup-shaped clamping member and deformable means formed of a resiliently deformable material, said clamping member being internally dimensioned to removably receive said deformable member and having an opening through a base portion thereof for freely receiving at least said grinding element, said clamping member being removably fixed to said front end for resiliently deforming said deformable member into clamping surface engagement with said grinding element whereby to releasably clamp said grinding element for rotation with said drive tube.

5. In a grinding tool according to claim 4, wherein said deformable member is a bushing having a through opening dimensioned to loosely receive said grinding element and having a cam follower surface, said clamping member base portion defines a cam surface, and said clamping member is threadable onto said front end of said drive tube for clamping said bushing therebetween, whereupon said cam and cam follower surfaces cooperate to resiliently deform said bushing radially into clamping surface engagement with said grinding element.

6. In a grinding tool according to claim 4, wherein said deformable member is an O-ring formed of a resiliently deformable material, said O-ring having an internal diameter dimensioned for snug fitting rolling engagement with said grinding element when not axially compressed, and said clamping means additionally includes a wear bushing removably fitted within said clamping member and having a through opening dimensioned to slideably accommodate said grinding element, said wear bushing being formed of a relatively hard abrasive-resistant plastic material, and said through opening of said wear bushing is rearwardly and outwardly flared to define an essentially conically shaped guide surface disposed for clamping engaging said O-ring. i

7. In a grinding tool according to claim 4, wherein said casing has another wall having another opening disposed in axial alignment with and spaced from a rear end of said drive tube, a cup-shaped guard member is fixed externally of said casing in alignment with said other opening, and said other opening and said cupshaped guard member are dimensioned to freely receive an end of grinding element projecting rearwardly through said rear end of said drive tube.

8. In a grinding tool according to claim 7, wherein said means for rotating said drive tube includes a drive pulley disposed within said casing adjacent said other wall, an endless drive belt trained about said drive pulley and said rear end of said drive tube, and a motor fixed to said other Wall exteriorly of said casing and drivingly connected to said drive pulley through said other wall.

9. In a grinding tool according to claim 4, wherein said locking means additionally includes a reducing sleeve slidably fitted within said drive tube and dimensioned to freely accommodate said grinding element therewithin to removably extend through a front end portion thereof, said front end portion defining a radial surface dimensioned to abut against said front end of said drive tube, and said clamping member cooperating with said front end to axially clamp said deformable member and said front end portion therebetween, whereby said deformable member is resiliently deformed and said reducing sleeve is constrained for rotation with said drive tube.

10. In a grinding tool according to claim 4, wherein said locking means additionally includes sleeve means internally dimensioned to slidably receive said grinding element and being arranged within said clamping member to extend forwardly through said opening thereof, said clamping member releasably maintaining said sleeve means in deforming engagement with said deformable member, and said sleeve means being formed of a relatively hard abrasive-resistant plastic material.

for cushioning transversely directed vibratory movements of said end of said grinding element relative to said base portion of said clamping member forwardly of a point at which said grinding element is clampingly engaged by said deformable member.

11. A grinding tool comprising in combination:

a hollow casing having an opening through awall thereof;

an elongated drive tube;

means for supporting said drive tube for rotation within said casing with a front end of said drive tube projecting outwardly through said casing wall opening;

means for rotating said drive tube;

a reducing sleeve for selectively fitting said grinding tool with an elongated grinding element support spindle of a smaller diameter than said drive tube, said reducing sleeve being externally dimensioned to be removably slide fitted within said drive tube for positioning an enlarged front end portion thereof in axial abutting engagement with said front end, said sleeve being internally dimensioned 1. l to slidably receive said smaller diameter grinding element support spindle to removably extend through said front end portion;

deformable means formed of a resiliently deformable material; and

a clamping member internally dimensioned to removably receive said deformable member and said front end portion, said clamping member having an opening through a base portion thereof for freely receiving a front end of said grinding element support spindle, and said clamping member being refor rotation with said drive tube. 

1. In a grinding tool adapted for use with an elongated relatively uniform diameter grinding element having an end adapted to be progressively worn away be engagement with a workpiece during operation of said grinding tool, the combination comprising: a rotatably supported drive tube, said drive tube being dimensioned to freely accommodate said grinding element therewithin to removably extend through a front end thereof; means for rotating said drive tube; and locking means carried by said front end for releasably clamping said grinding element intermediate opposite ends thereof for rotation with said drive tube, whereby said end of said grinding element normally projects forwardly of said front end beyond said locking means during operation of said tool, said locking means including a deformable member formed or a resiliently deformable material and clamping means carried on said front end for resiliently deforming said deformable member into clamping surface engagement with said grinding element whereby to releasably clamp said grinding element for rotation with said drive tube, said clamping means including a cup shaped clamping member having an opening through a base portion thereof and sleeve means slidably receiving said grinding element and being arranged within said clamping member to extend forwardly through said opening, said clamping member having a rim portion threadably attached to said front end of said drive tube for releasably maintaining said sleeve means in deforming engagement with said deformable member, and said sleeve means being formed at least in part of a relatively hard abrasive-resistant plastic material thereby to cushion transversely directed vibratory movements of said end of said grinding element relative to said base portion of said clamping member forwardly of the point at which said grinding element is clampingly engaged by sAid deformable member.
 2. In a grinding tool adapted for use with an elongated relatively uniform diameter grinding element having an end adapted to be progressively worn away by engagement with a workpiece during operation of said grinding tool, the combination comprising: a rotatably supported drive tube; means for rotating said drive tube; and locking means carried by a front end of said drive tube for releasably clamping said grinding element intermediate opposite ends thereof for rotation with said drive tube, whereby said end of said grinding element normally projects forwardly of said front end beyond said locking means during operation of said tool, said locking means includes a reducing sleeve, a generally cup-shaped clamping member, and a sleeve bushing formed of a resiliently deformable material, said reducing sleeve being slidably and removably insertable within said drive tube and dimensioned to freely accommodate said grinding element therewithin to removably extend through a front end portion thereof, said front end portion defining a radial surface dimensioned to abut against said front end of said drive tube inwardly of an outer surface thereof, said brushing having a through opening dimensioned to loosely receive said grinding element and having a concentrically arranged cam follower surface, said clamping member being internally dimensioned to removably receive said bushing and said front end portion and having an opening through a base portion thereof sized to at least freely receive said grinding element, said clamping member base portion defining a cam surface, said clamping member having a rim portion adjustably threaded onto said front end of said drive tube whereby to cooperate with said front end to axially clamp said bushing against said front end portion and said front end poortion against said front end of said drive tube, whereby said cam and cam follower surfaces cooperate to resiliently deform said bushing radially into clamping surface engagement with said grinding element and said grinding element and reducing sleeve are constrained for rotation with said drive tube.
 3. In a grinding tool adapted for use with an elongated relatively uniform diameter grinding element having an end adapted to be progressively worn away by engagement with a workpiece during operation of said grinding tool, the combination comprising: a rotatably supported drive tube; means for rotating said drive tube; and locking means carried by a front end of said drive tube for releasably clamping said grinding element intermediate opposite ends thereof for rotation with said drive tube, whereby said end of said grinding element normally projects forwardly of said front end beyond said locking means during operation of said tool, said locking means including a reducing sleeve, a cup-shaped clamping member, a sleeve bushing and an O-ring formed of resiliently deformable material, said reducing sleeve being slidably and removably insertable within said drive tube and dimensioned to freely accommodate said grinding element therewithin to removably extend through a front end portion thereof, said front end portion defining a radial surface dimensioned to abut against said front end of said drive tube inwardly of an outer surface thereof, said sleeve bushing having a sleeve portion formed of a relatively hard abrasive-resistant plastic material and dimensioned to loosely receive said grinding element and an enlarged base portion, said clamping member being internally dimensioned to removably receive said enlarged base portion and said front end portion and having an opening through a base portion thereof for removably receiving said sleeve portion, said O-ring being arranged intermediate facing surfaces of said enlarged base portion and said front end portion and being dimensioned to snugly receive said grinding element, one of said facing surfaces having an essentially conically shaped guide surface arranged to axially engage said O-ring, said clamping member having a rim portion adjustably threaded onto said front end whereby to cooperate with said front end to axially clamp said front end portion against said front end and said O-ring between said guide surface and another of said facing surfaces for resiliently deforming said O-ring radially inwardly into clamping engagement with said grinding element and for clamping said reducing sleeve, sleeve bushing and grinding element for rotation with said drive tube, and said sleeve portion cushioning transversely directed vibratory movement of said end of said grinding element relative to said base portion of said clamping member forwardly of the point at which said grinding element is clampingly engaged by said O-ring.
 4. In a grinding tool adapted for use with an elongated relatively uniformed diameter grinding element having an end adapted to be progressively worn away by engagement with a workpiece during operation of said grinding tool, which comprises in combination: a hollow casing having an opening through a wall thereof; an elongated drive tube, said drive tube being dimensioned to freely accommodate said grinding element therewithin to removably extend through a front end thereof; means for supporting said drive tube for rotation within said casing with said front end of said drive tube projecting outwardly through said casing wall opening; means for rotating said drive tube; and locking means carried by said front end of said drive tube for releasably clamping said grinding element intermediate opposite ends thereof for rotation with said drive tube wherein said grinding element normally projects forwardly of said front end beyond said locking means during operation of said tool, said locking means includes a cup-shaped clamping member and deformable means formed of a resiliently deformable material, said clamping member being internally dimensioned to removably receive said deformable member and having an opening through a base portion thereof for freely receiving at least said grinding element, said clamping member being removably fixed to said front end for resiliently deforming said deformable member into clamping surface engagement with said grinding element whereby to releasably clamp said grinding element for rotation with said drive tube.
 5. In a grinding tool according to claim 4, wherein said deformable member is a bushing having a through opening dimensioned to loosely receive said grinding element and having a cam follower surface, said clamping member base portion defines a cam surface, and said clamping member is threadable onto said front end of said drive tube for clamping said bushing therebetween, whereupon said cam and cam follower surfaces cooperate to resiliently deform said bushing radially into clamping surface engagement with said grinding element.
 6. In a grinding tool according to claim 4, wherein said deformable member is an O-ring formed of a resiliently deformable material, said O-ring having an internal diameter dimensioned for snug fitting ''''rolling'''' engagement with said grinding element when not axially compressed, and said clamping means additionally includes a wear bushing removably fitted within said clamping member and having a through opening dimensioned to slideably accommodate said grinding element, said wear bushing being formed of a relatively hard abrasive-resistant plastic material, and said through opening of said wear bushing is rearwardly and outwardly flared to define an essentially conically shaped guide surface disposed for clamping engaging said O-ring.
 7. In a grinding tool according to claim 4, wherein said casing has another wall having another opening disposed in axial alignment with and spaced from a rear end of said drive tube, a cup-shaped guard member is fixed externally of said casing in alignment with said other opening, and said other opening and said cup-shaped guard member are dimensioned to freely receive an enD of grinding element projecting rearwardly through said rear end of said drive tube.
 8. In a grinding tool according to claim 7, wherein said means for rotating said drive tube includes a drive pulley disposed within said casing adjacent said other wall, an endless drive belt trained about said drive pulley and said rear end of said drive tube, and a motor fixed to said other wall exteriorly of said casing and drivingly connected to said drive pulley through said other wall.
 9. In a grinding tool according to claim 4, wherein said locking means additionally includes a reducing sleeve slidably fitted within said drive tube and dimensioned to freely accommodate said grinding element therewithin to removably extend through a front end portion thereof, said front end portion defining a radial surface dimensioned to abut against said front end of said drive tube, and said clamping member cooperating with said front end to axially clamp said deformable member and said front end portion therebetween, whereby said deformable member is resiliently deformed and said reducing sleeve is constrained for rotation with said drive tube.
 10. In a grinding tool according to claim 4, wherein said locking means additionally includes sleeve means internally dimensioned to slidably receive said grinding element and being arranged within said clamping member to extend forwardly through said opening thereof, said clamping member releasably maintaining said sleeve means in deforming engagement with said deformable member, and said sleeve means being formed of a relatively hard abrasive-resistant plastic material for cushioning transversely directed vibratory movements of said end of said grinding element relative to said base portion of said clamping member forwardly of a point at which said grinding element is clampingly engaged by said deformable member.
 11. A grinding tool comprising in combination: a hollow casing having an opening through a wall thereof; an elongated drive tube; means for supporting said drive tube for rotation within said casing with a front end of said drive tube projecting outwardly through said casing wall opening; means for rotating said drive tube; a reducing sleeve for selectively fitting said grinding tool with an elongated grinding element support spindle of a smaller diameter than said drive tube, said reducing sleeve being externally dimensioned to be removably slide fitted within said drive tube for positioning an enlarged front end portion thereof in axial abutting engagement with said front end, said sleeve being internally dimensioned to slidably receive said smaller diameter grinding element support spindle to removably extend through said front end portion; deformable means formed of a resiliently deformable material; and a clamping member internally dimensioned to removably receive said deformable member and said front end portion, said clamping member having an opening through a base portion thereof for freely receiving a front end of said grinding element support spindle, and said clamping member being removably fixed to said front end and cooperating therewith for axially clamping said deformable member and said front end portion therebetween for resiliently deforming said deformable member into clamping surface engagement with said grinding element support spindle intermediate opposite ends thereof and for releasably constraining said sleeve and said grinding element support spindle for rotation with said drive tube. 